The present invention is related to a character generator read only memory (CGROM) testing device. The character pattern data of predetermined characters are previously recorded in the EPROM. A first IC compares the data of the EPROM with the character code output by the CGROM so as to judge whether the CGROM of the controlling IC of PCB is defective or not.
A conventional liquid crystal display module (LCM) sometimes fails to fully display characters. This is generally because that the character generator read only memory (CGROM) of the controlling IC in the LCM is defective. The defective CGROM often results from that the IC manufacturer fails to entirely test the CGROM. The existent test is mainly visual test. In general, there are about 180xcx9c240 inbuilt characters of the CGROM and the LCM can display multiple different characters to form a picture. With 5xc3x977 character exemplified, each character is divided into 35 small square blocks. In case each character should be completely checked, all the small blocks must be visually checked. Generally one picture will have several to several decades of different characters. Accordingly, it will cost several to several decades of seconds to completely check a picture. When many pictures need to be checked, it often takes several minutes to complete the check. Therefore, the efficiency of check is very low. In addition, the visual check often results in error and incomplete check.
It is therefore a primary object of the present invention to provide a CGROM testing device. After each character to be tested is converted into seven 8-bit hexadecimal data, the data are previously recorded in the EPROM. The display panel is driven by controlling IC of PCB to display characters of CGROM to be tested. Probes are used to contact with the COM and SEG test points on the PCB to obtain analog signals. By means of the sequential selection of the analog multiplex selection circuit and the conversion of the analog-to-digital converting circuit, the first IC compares the character pattern data of predetermined characters inbuilt in the EPROM with the digital data so as to judge whether the character of the CGROM is problematic or not. A tester can easily judge whether the CGROM of the PCB is problematic from the green light, red light and buzzer and the display panel. Accordingly, it only takes several seconds to complete the test of one PCB. The labor is saved and the test can be quickly completed. Moreover, the man-made error can be minimized.
The present invention can be best understood through the following description and accompanying drawings wherein: